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Re: [softrock40] Poor sensitivity on RXTX Ensemble during testing

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  • Pete MI0VAX
    As has already been said, these components are selected for the bands required. Therefore I would have expected peak sensitivity to be at somewhere between the
    Message 1 of 10 , Nov 3, 2011
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      As has already been said, these components are selected for the bands required. Therefore I would have expected peak sensitivity to be at somewhere between the bottom of 17m and the top of 10m

      It had crossed my mind to take a winding or two off L2 and L3 - I may try this when I get time, thought i'd post a question here first to see if there was a common problem.

      I have sorted through the rest of the capacitors, and can only find one other that again looks like the one I have fitted. None of the caps have 82 on them
       
      Cheers,

      Pete

      Mi0VAX


      > Just got the rx section of my RXTX Ensemble built,
      > Turns out although i've got it built for 15/12/10m that peak sensitivity
      > is
      > at approx 13.2MHz with a mds of 123dBm whereas at 10m the mds is 110dBm
      >

      I don't know what to expect but I'd think it should be more even.
      Sensitivity is needed at the high end.


      > Have checked the caps, all appear to
      > be correct apart from C27 which I am unable to read -

      As this is selected according to the frequency range I'd make sure the
      correct one is fitted. You must have some left over, do they show the
      expected markings? Get one the correct value.

      Again, Mike says your figures are good. The Softrock is not over-sensitive
      like so many commercial radios. It does need a good antenna.

      73 Alan G4ZFQ




      --
      Peter Holmes

      Mi0VAX

      Vice Secretary
      Mid-Ulster Amateur Radio Club

    • Alan
      ... From: Pete Subject: Re: [softrock40] Poor sensitivity on RXTX Ensemble during testing ... other that again looks like the one I have fitted. None of the
      Message 2 of 10 , Nov 3, 2011
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        ----- Original Message -----
        From: "Pete
        Subject: Re: [softrock40] Poor sensitivity on RXTX Ensemble during testing


        >I have sorted through the rest of the capacitors, and can only find one
        other that again looks like the one I have fitted. None of the caps have 82
        on them

        Yes, but just make sure the correct value is there before you do anything
        else. Fit one that IS marked.

        73 Alan G4ZFQ
      • Orin
        Well, I did put mine on the VNWA and took a look at just the filter output (the secondary of T4 was convenient as it s not installed yet). Results were
        Message 3 of 10 , Nov 3, 2011
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          Well, I did put mine on the VNWA and took a look at just the filter output (the secondary of T4 was convenient as it's not installed yet). Results were inconclusive. I suspect that I'll have to install T4 and measure at L4/C39 instead to get a better idea for RX. I did have a gentle peak at about 30 MHz and a big dip at about 13 MHz. Here is a link to the trace - maybe it will work ;)

          https://picasaweb.google.com/lh/photo/TSP25NK0VZUsWN1c_UWyiFc5ZMJfUTjvt-kVq_Nor9U?feat=directlink

          I'd be more concerned about losses on TX... I should have measured S22 and S12 as well. Perhaps tomorrow night.

          I did hook up the signal generator and took a look with SDR Console. MDS is about -120 dBm at 20 and 28 MHz, though SDR Console isn't playing nice with the Si570 and I have to use CFGSR to set the frequency to what I want to look at, then run SDR Console.

          Orin, KJ7HQ.

          --- In softrock40@yahoogroups.com, Pete MI0VAX <petemi0vax@...> wrote:
          >
          > As has already been said, these components are selected for the bands
          > required. Therefore I would have expected peak sensitivity to be at
          > somewhere between the bottom of 17m and the top of 10m
          >
          > It had crossed my mind to take a winding or two off L2 and L3 - I may try
          > this when I get time, thought i'd post a question here first to see if
          > there was a common problem.
          >
          > I have sorted through the rest of the capacitors, and can only find one
          > other that again looks like the one I have fitted. None of the caps have 82
          > on them
          >
          > Cheers,
          >
          > Pete
          >
          > Mi0VAX
          >
          >
          > > > Just got the rx section of my RXTX Ensemble built,
          > > > Turns out although i've got it built for 15/12/10m that peak sensitivity
          > > > is
          > > > at approx 13.2MHz with a mds of 123dBm whereas at 10m the mds is 110dBm
          > > >
          > >
          > > I don't know what to expect but I'd think it should be more even.
          > > Sensitivity is needed at the high end.
          > >
          > >
          > > > Have checked the caps, all appear to
          > > > be correct apart from C27 which I am unable to read -
          > >
          > > As this is selected according to the frequency range I'd make sure the
          > > correct one is fitted. You must have some left over, do they show the
          > > expected markings? Get one the correct value.
          > >
          > > Again, Mike says your figures are good. The Softrock is not over-sensitive
          > > like so many commercial radios. It does need a good antenna.
          > >
          > > 73 Alan G4ZFQ
          > >
          > >
          > >
          >
          >
          >
          > --
          > *Peter Holmes*
          >
          > Mi0VAX
          >
          > Vice Secretary
          > Mid-Ulster Amateur Radio Club <http://www.muarc.com>
          >
        • Pete MI0VAX
          Hi again Orin & all Fitted a known 82pf cap and am still experiencing the same issues. Considering this may be a similar problem to what you are experiencing
          Message 4 of 10 , Nov 8, 2011
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            Hi again Orin & all

            Fitted a known 82pf cap and am still experiencing the same issues.

            Considering this may be a similar problem to what you are experiencing on TX in a recent post?

            Look forward to your thoughts

            Pete

            Mi0VAX

            On Fri, Nov 4, 2011 at 4:23 AM, Orin <orin.eman@...> wrote:
             

            Well, I did put mine on the VNWA and took a look at just the filter output (the secondary of T4 was convenient as it's not installed yet). Results were inconclusive. I suspect that I'll have to install T4 and measure at L4/C39 instead to get a better idea for RX. I did have a gentle peak at about 30 MHz and a big dip at about 13 MHz. Here is a link to the trace - maybe it will work ;)

            https://picasaweb.google.com/lh/photo/TSP25NK0VZUsWN1c_UWyiFc5ZMJfUTjvt-kVq_Nor9U?feat=directlink

            I'd be more concerned about losses on TX... I should have measured S22 and S12 as well. Perhaps tomorrow night.

            I did hook up the signal generator and took a look with SDR Console. MDS is about -120 dBm at 20 and 28 MHz, though SDR Console isn't playing nice with the Si570 and I have to use CFGSR to set the frequency to what I want to look at, then run SDR Console.

            Orin, KJ7HQ.



            --- In softrock40@yahoogroups.com, Pete MI0VAX <petemi0vax@...> wrote:
            >
            > As has already been said, these components are selected for the bands
            > required. Therefore I would have expected peak sensitivity to be at
            > somewhere between the bottom of 17m and the top of 10m
            >
            > It had crossed my mind to take a winding or two off L2 and L3 - I may try
            > this when I get time, thought i'd post a question here first to see if
            > there was a common problem.
            >
            > I have sorted through the rest of the capacitors, and can only find one
            > other that again looks like the one I have fitted. None of the caps have 82
            > on them
            >
            > Cheers,
            >
            > Pete
            >
            > Mi0VAX
            >
            >
            > > > Just got the rx section of my RXTX Ensemble built,
            > > > Turns out although i've got it built for 15/12/10m that peak sensitivity
            > > > is
            > > > at approx 13.2MHz with a mds of 123dBm whereas at 10m the mds is 110dBm
            > > >
            > >
            > > I don't know what to expect but I'd think it should be more even.
            > > Sensitivity is needed at the high end.
            > >
            > >
            > > > Have checked the caps, all appear to
            > > > be correct apart from C27 which I am unable to read -
            > >
            > > As this is selected according to the frequency range I'd make sure the
            > > correct one is fitted. You must have some left over, do they show the
            > > expected markings? Get one the correct value.
            > >
            > > Again, Mike says your figures are good. The Softrock is not over-sensitive
            > > like so many commercial radios. It does need a good antenna.
            > >
            > > 73 Alan G4ZFQ
            > >
            > >
            > >
            >
            >
            >



          • Orin
            Pete, I don t think you should see much difference at all in sensitivity between 20 and 30 MHz given my latest results. I took L2 & L3 off and measured them on
            Message 5 of 10 , Nov 8, 2011
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              Pete,

              I don't think you should see much difference at all in sensitivity between 20 and 30 MHz given my latest results.

              I took L2 & L3 off and measured them on my MFJ 259. 0.48 and 0.50 uH! They are supposed to be 0.36 uH. (I do trust the MFJ to be in the ballpark, I've checked it against sweeping toroids on the VNWA before.) I took two turns off each and they were then both 0.35 to 0.37 uH. I put L3 & L2 back on the board and removed the RX coupling capacitor. Things are much better.

              Loss is now 0.34 dB at 21 MHz, 0.4 dB at 25M Hz and 0.48 dB at 30 MHz (according to the VNWA). I imported the Elsie data into the VNWA and ran another scan. Here is my actual vs Elsie scan:

              https://picasaweb.google.com/lh/photo/Ujjps0q183ySKsaP29mDm4LS1FToz1TiCJzHAUEj7Cg?feat=directlink

              I also checked using the MFJ 259 as a signal source and the 8568A spectrum analyzer.

              https://picasaweb.google.com/lh/photo/XojAO-yLP2W92fthfyNV9YLS1FToz1TiCJzHAUEj7Cg?feat=directlink

              Top red trace is MFJ 259 direct to spectrum analyzer, bottom green trace is through the filter. I had the SA on Max Hold and swept the frequency on the MFJ. Loss is about 0.5 dB at 29 MHz and the MFJ 259 was showing 1.1 SWR.

              I think that's good enough, though I might try squeezing the turns on the toroids a little closer together to see if I can get closer to the Elsie curve.

              So I'd definitely suggest taking a couple of turns off L2 and L3! I didn't get chance to run MDS checks again tonight. I have to put the RX coupling capacitor back in first.

              Orin.

              --- In softrock40@yahoogroups.com, Pete MI0VAX <petemi0vax@...> wrote:
              >
              > Hi again Orin & all
              >
              > Fitted a known 82pf cap and am still experiencing the same issues.
              >
              > Considering this may be a similar problem to what you are experiencing on
              > TX in a recent post?
              >
              > Look forward to your thoughts
              >
              > Pete
              >
              > Mi0VAX
              >
              > On Fri, Nov 4, 2011 at 4:23 AM, Orin <orin.eman@...> wrote:
              >
              > > **
              > >
              > >
              > > Well, I did put mine on the VNWA and took a look at just the filter output
              > > (the secondary of T4 was convenient as it's not installed yet). Results
              > > were inconclusive. I suspect that I'll have to install T4 and measure at
              > > L4/C39 instead to get a better idea for RX. I did have a gentle peak at
              > > about 30 MHz and a big dip at about 13 MHz. Here is a link to the trace -
              > > maybe it will work ;)
              > >
              > >
              > > https://picasaweb.google.com/lh/photo/TSP25NK0VZUsWN1c_UWyiFc5ZMJfUTjvt-kVq_Nor9U?feat=directlink
              > >
              > > I'd be more concerned about losses on TX... I should have measured S22 and
              > > S12 as well. Perhaps tomorrow night.
              > >
              > > I did hook up the signal generator and took a look with SDR Console. MDS
              > > is about -120 dBm at 20 and 28 MHz, though SDR Console isn't playing nice
              > > with the Si570 and I have to use CFGSR to set the frequency to what I want
              > > to look at, then run SDR Console.
              > >
              > > Orin, KJ7HQ.
              > >
              > >
              > > --- In softrock40@yahoogroups.com, Pete MI0VAX <petemi0vax@> wrote:
              > > >
              > > > As has already been said, these components are selected for the bands
              > > > required. Therefore I would have expected peak sensitivity to be at
              > > > somewhere between the bottom of 17m and the top of 10m
              > > >
              > > > It had crossed my mind to take a winding or two off L2 and L3 - I may try
              > > > this when I get time, thought i'd post a question here first to see if
              > > > there was a common problem.
              > > >
              > > > I have sorted through the rest of the capacitors, and can only find one
              > > > other that again looks like the one I have fitted. None of the caps have
              > > 82
              > > > on them
              > > >
              > > > Cheers,
              > > >
              > > > Pete
              > > >
              > > > Mi0VAX
              > > >
              > > >
              > > > > > Just got the rx section of my RXTX Ensemble built,
              > > > > > Turns out although i've got it built for 15/12/10m that peak
              > > sensitivity
              > > > > > is
              > > > > > at approx 13.2MHz with a mds of 123dBm whereas at 10m the mds is
              > > 110dBm
              > > > > >
              > > > >
              > > > > I don't know what to expect but I'd think it should be more even.
              > > > > Sensitivity is needed at the high end.
              > > > >
              > > > >
              > > > > > Have checked the caps, all appear to
              > > > > > be correct apart from C27 which I am unable to read -
              > > > >
              > > > > As this is selected according to the frequency range I'd make sure the
              > > > > correct one is fitted. You must have some left over, do they show the
              > > > > expected markings? Get one the correct value.
              > > > >
              > > > > Again, Mike says your figures are good. The Softrock is not
              > > over-sensitive
              > > > > like so many commercial radios. It does need a good antenna.
              > > > >
              > > > > 73 Alan G4ZFQ
              > > > >
              > > > >
              > > > >
              > > >
              > > >
              > > >
              > >
              > >
              > >
              >
            • Pete MI0VAX
              Now i m really baffled! Took 2 turns from L2 and L3 but now the best sensitivity is at 11mhz :o Since last time I have discovered a few settings in HDSDR that
              Message 6 of 10 , Nov 13, 2011
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                Now i'm really baffled!

                Took 2 turns from L2 and L3 but now the best sensitivity is at 11mhz :o\

                Since last time I have discovered a few settings in HDSDR that I wasnt aware of, now I can inject a -129.8dBm signal in at 11.5mhz and see it on the fft

                At 28.5mhz the signal needs to be -118dBm to be visible

                Can anyone explain why this should be?

                Pete

                On Wed, Nov 9, 2011 at 7:57 AM, Orin <orin.eman@...> wrote:
                 

                Pete,

                I don't think you should see much difference at all in sensitivity between 20 and 30 MHz given my latest results.

                I took L2 & L3 off and measured them on my MFJ 259. 0.48 and 0.50 uH! They are supposed to be 0.36 uH. (I do trust the MFJ to be in the ballpark, I've checked it against sweeping toroids on the VNWA before.) I took two turns off each and they were then both 0.35 to 0.37 uH. I put L3 & L2 back on the board and removed the RX coupling capacitor. Things are much better.

                Loss is now 0.34 dB at 21 MHz, 0.4 dB at 25M Hz and 0.48 dB at 30 MHz (according to the VNWA). I imported the Elsie data into the VNWA and ran another scan. Here is my actual vs Elsie scan:

                https://picasaweb.google.com/lh/photo/Ujjps0q183ySKsaP29mDm4LS1FToz1TiCJzHAUEj7Cg?feat=directlink

                I also checked using the MFJ 259 as a signal source and the 8568A spectrum analyzer.

                https://picasaweb.google.com/lh/photo/XojAO-yLP2W92fthfyNV9YLS1FToz1TiCJzHAUEj7Cg?feat=directlink

                Top red trace is MFJ 259 direct to spectrum analyzer, bottom green trace is through the filter. I had the SA on Max Hold and swept the frequency on the MFJ. Loss is about 0.5 dB at 29 MHz and the MFJ 259 was showing 1.1 SWR.

                I think that's good enough, though I might try squeezing the turns on the toroids a little closer together to see if I can get closer to the Elsie curve.

                So I'd definitely suggest taking a couple of turns off L2 and L3! I didn't get chance to run MDS checks again tonight. I have to put the RX coupling capacitor back in first.

                Orin.



                --- In softrock40@yahoogroups.com, Pete MI0VAX <petemi0vax@...> wrote:
                >
                > Hi again Orin & all
                >
                > Fitted a known 82pf cap and am still experiencing the same issues.
                >
                > Considering this may be a similar problem to what you are experiencing on
                > TX in a recent post?
                >
                > Look forward to your thoughts
                >
                > Pete
                >
                > Mi0VAX
                >
                > On Fri, Nov 4, 2011 at 4:23 AM, Orin <orin.eman@...> wrote:
                >
                > > **

                > >
                > >
                > > Well, I did put mine on the VNWA and took a look at just the filter output
                > > (the secondary of T4 was convenient as it's not installed yet). Results
                > > were inconclusive. I suspect that I'll have to install T4 and measure at
                > > L4/C39 instead to get a better idea for RX. I did have a gentle peak at
                > > about 30 MHz and a big dip at about 13 MHz. Here is a link to the trace -
                > > maybe it will work ;)
                > >
                > >
                > > https://picasaweb.google.com/lh/photo/TSP25NK0VZUsWN1c_UWyiFc5ZMJfUTjvt-kVq_Nor9U?feat=directlink
                > >
                > > I'd be more concerned about losses on TX... I should have measured S22 and
                > > S12 as well. Perhaps tomorrow night.
                > >
                > > I did hook up the signal generator and took a look with SDR Console. MDS
                > > is about -120 dBm at 20 and 28 MHz, though SDR Console isn't playing nice
                > > with the Si570 and I have to use CFGSR to set the frequency to what I want
                > > to look at, then run SDR Console.
                > >
                > > Orin, KJ7HQ.
                > >
                > >
                > > --- In softrock40@yahoogroups.com, Pete MI0VAX <petemi0vax@> wrote:
                > > >
                > > > As has already been said, these components are selected for the bands
                > > > required. Therefore I would have expected peak sensitivity to be at
                > > > somewhere between the bottom of 17m and the top of 10m
                > > >
                > > > It had crossed my mind to take a winding or two off L2 and L3 - I may try
                > > > this when I get time, thought i'd post a question here first to see if
                > > > there was a common problem.
                > > >
                > > > I have sorted through the rest of the capacitors, and can only find one
                > > > other that again looks like the one I have fitted. None of the caps have
                > > 82
                > > > on them
                > > >
                > > > Cheers,
                > > >
                > > > Pete
                > > >
                > > > Mi0VAX
                > > >
                > > >
                > > > > > Just got the rx section of my RXTX Ensemble built,
                > > > > > Turns out although i've got it built for 15/12/10m that peak
                > > sensitivity
                > > > > > is
                > > > > > at approx 13.2MHz with a mds of 123dBm whereas at 10m the mds is
                > > 110dBm
                > > > > >
                > > > >
                > > > > I don't know what to expect but I'd think it should be more even.
                > > > > Sensitivity is needed at the high end.
                > > > >
                > > > >
                > > > > > Have checked the caps, all appear to
                > > > > > be correct apart from C27 which I am unable to read -
                > > > >
                > > > > As this is selected according to the frequency range I'd make sure the
                > > > > correct one is fitted. You must have some left over, do they show the
                > > > > expected markings? Get one the correct value.
                > > > >
                > > > > Again, Mike says your figures are good. The Softrock is not
                > > over-sensitive
                > > > > like so many commercial radios. It does need a good antenna.
                > > > >
                > > > > 73 Alan G4ZFQ
                > > > >
                > > > >
                > > > >
                > > >
                > > >
                > > >
                > >
                > >
                > >
                >





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